The present invention relates to an electrochemical generator and methods of using the same to generate a biocidal solution.
Biocidal solutions are often needed as a general disinfectant in various fields, such as in water decontamination, dental, medical and food preparation environments. For example, in hospitals, it is important to provide appropriate levels of sterility, particularly in operating rooms and other situations where invasive treatments are performed. Surgical instruments and other apparatus must be sterilized or disinfected, depending on their application, before use in order to reduce the risk of bacterial infection. One method of sterilization is the application of heat and pressure in an autoclave. However, this is not suitable for some medical apparatus, such as heat-sensitive endoscopes.
A typical method employed for reprocessing heat sensitive instruments involves the use of chemical biocides, such as glutaraldehyde. This can be unsatisfactory due to improper or incomplete disinfection. Furthermore, exposure to glutaraldehyde fumes can cause asthma and dermatitis in healthcare staff. Also, glutaraldehyde is believed to have relatively low sporicidal activity. Moreover, other disinfectants, such as chlorine dioxide and peracetic acid may suffer from similar handling problems as glutaraldehyde.
For some years, it has been known that electrochemical activation of brine or a saturated saline solution produces an electrochemically activated solution that is suitable for many applications, including general disinfection in medical and veterinary applications and the sterilization of heat-sensitive endoscopes, among other uses. There has been a recent interest in the use of an electrochemically activated solution as a disinfectant because of its rapid and highly biocidal activity against a wide range of bacteria, fungi, viruses and spores. Also, an electrochemically activated solution is an effective sterilizing cold non-toxic solution that is free from highly toxic chemicals, thereby presenting reduced handling risk.
Certain electrolytic cells are known to operate by a process described in commonly-assigned U.S. Pat. No. 6,632,347 to Buckley et al., the contents of which are incorporated herein in their entirety. Referring to FIG. 1, the formation of a biocidal liquid as described in this patent can be divided into three main processing stages, namely an input and pre-processing stage, a production stage, and a storage and dispensing stage.
In the first (inputs and pre-processing) stage, there is an input of potable water which, for the purpose of generating a saline solution for use in the electrolytic cell, can first be passed through a water softener zone where excessive magnesium and calcium ions can be removed. The softened water can then be passed into a process water buffer zone where it can be held until required for use in the production of brine. Potable water input can also be passed directly to the storage and dispensing stage for use in the preparation of bacteria-free rinse water (in which case the water may not need to be softened).
The first stage also includes a salt (halide salt or ionic salt, e.g. NaCl) input to a brine generation zone where a concentrated salt solution is made up from the salt and the softened water obtained via the process water buffer zone. A further input can be provided for additional agents, such as a corrosion inhibitor, used to condition output solution produced by the process. The conditioner can be passed to a conditioner storage zone where it can be held until required.
Turning to the second (production) stage, this can include a constant salinity subsystem in which a saline solution of substantially constant concentration is produced by dilution of the brine from the brine generation zone with softened water from the process water buffer zone to the desired concentration. The resulting saline solution can then be passed from the constant salinity subsystem to one or more electrolytic cells, each including cathode and anode chambers (not shown), and across which a substantially constant electric current can be applied. The applied electric current can be maintained constant via an energy control and monitoring zone.
Catholyte and anolyte are produced from the cathode and anode chambers respectively as a result of the electrochemical treatment of the saline solution in the cells. A portion of the catholyte can be re-circulated, directly or indirectly, into the anode chamber to control pH. Anolyte and any catholyte which is not re-circulated to the anode chamber can both be dealt with in the third (storage and dispensing) stage. In particular, catholyte which is not re-circulated can be directed to waste and anolyte, otherwise referred to as the output solution, can be passed to a buffer and quality subsystem. The output solution can be tested in the buffer and quality subsystem and, if it fails to meet the quality standards, it can also be directed to waste. If the output solution falls within specification, a quantity of conditioner, such as a corrosion inhibitor, can be added to it in the buffer subsystem and the output solution can then be permitted to pass either into an output solution storage zone from where it is subsequently dispensed for use or into a rinse water subsystem.
Output solution directed to the rinse water subsystem can be diluted with potable water from the potable water input and can then be passed to a rinse water storage zone from where it is subsequently dispensed.
Information on the various processing stages and the ability to interact with the process as described in U.S. Pat. No. 6,632,347 can be provided by means of a user interface and a service interface. The service interface also provides for remote access to the process, enabling an off-site engineer to obtain information on and make adjustments to the processing in each of the three stages.
Fluctuations in the temperature of the potable water causes a corresponding change in the temperature and conductivity of the brine solution that is formed from the potable water. The corresponding change in conductivity of the brine solution caused by the change in temperature affects the electrolytic process occurring in the electrochemical cells. Since conductivity of the brine solution is inversely related to resistance, a change in resistance effects current under Ohm's law (voltage (V) equals current (I) multiplied by resistance (R)). Aspects of the above relationships are described in commonly-assigned U.S. Patent Publication No. 2007/0017820 A1 of Anderson et al., the entire content of which is incorporated herein. Current in the electrolytic process should be maintained at the appropriate level to produce an output solution having the desired pH and available free chlorine (AFC) levels. Therefore, there is a need for a control system to compensate for the fluctuations in temperature of the input water and input brine solution.